Macbook Keyboard Not Working

Hi people, I realise there are a million 'I spilled liquid on my Macbook' threads but this one is actually about dealing with the effects of a spill. Being the moron that I am, I managed to spill a tiny amout of water on my Macbook, and I do mean tiny, it was probably less than a teaspoon amount. Nonetheless, it obviously didn't appreciate this.

After letting it dry out for 6 days, it appears that everything is working fine apart from the keyboard. On the login screen, it shows that stuff is being typed but when I'm on anything else nothing comes up. It works perfectly with a USB keyboard though.

So what I really just want to know is, is it just the keyboard that needs fixed, or have I likely done something worse to it? Also, if it is just the keyboard, any idea how much Apple charges to get that fixed?